1. Field of the Invention
Core flow is the pumping through a pipeline of a viscous waxy liquid such as oil, oil suspension, or oil emulsion in a core surrounded by a lighter viscosity liquid, such as water, at essentially the pressure drop of the lighter viscosity liquid. Normally, core flow is established by injecting water by separate means around a viscous or waxy oil being pumped in a pipeline. However, core flow can also be established by creating a certain shear rate for a certain length of time in a pipe flow to break an emulsion and create a water rich zone near the pipe wall. Any light viscosity liquid vehicle such as water, petroleum and its distillates may be employed as the annular liquid. Any high viscosity liquid such as petroleum and its by-products and mixtures thereof including solid components such as wax and foreign solids such as coal or concentrates, etc. may be employed for the core.
2. Description of the Prior Art
A substantial quantity of water is required for core flow. Inasmuch as crude oil as it is normally produced from oil wells contains some water, it may be a source of some or all of the water needed for core flow. This water is not difficult to separate from crude oil where the oil/water mixture contains only free water which will separate easily from the oil by merely providing a vessel in which water/oil phase separation occurs through the difference in gravities of the water and the oil. Where the water is dispersed through the oil in small particles, separation is more difficult inasmuch as minute particles of water are dispersed in the oil in a very stable condition due to the extensive area of interface between the water and the oil.
Even provided the water required can be obtained in part or in whole from the produced crude oil, there still remains a problem of disposal of the water once it has served its purpose in facilitating transport of the crude oil to a terminal station. Such water when gravity separated from the crude oil still contains at least some quantity of oil so that discharge into streams is unacceptable. Disposal into wells may also be undesirable, and further cleanup of the water may add substantially to the expense of the entire operation.
The present invention provides a solution to the above noted problems and presents alternative techniques for taking full advantage of water required for core flow, as will be apparent from the following description thereof.